Interdigital capacitive micromachined ultrasonic transducers for microfluidic applications

Directional generation and detection of Scholte waves in liquids and microfluidic channels by capacitive micromachined ultrasonic transducers (cMUTs) is reported. An interdigital transducer structure along with a phase excitation scheme is employed to enhance the directionality of Scholte interface waves in microfluidic environments. Experiments on the interdigital cMUTs show that a 5 finger-pair device in a water half-space has 12dB of directionality in generating Scholte waves at the design frequency of 10 MHz, which agrees with finite element analysis results. Transducers are demonstrated to perform bidirectional pumping in microfluidic channels with power levels in the milliwatt range. Interdigital cMUTs that are fabricated using low temperature processes can be used as compact ultrasonic transducers with integrated electronics for sensing and actuation in fluidic environment.